In most types of construction, particularly when firecode, it is necessary to completely block a passage through a wall that is provided to allow a conduit to pass through the wall, to stop any leakage, in particular of flame and vapors generated in a fire, through the wall.
A standard feedthrough assembly for a conduit has a wall formed with a throughgoing passage extending along an axis and having a radially inwardly directed wall surface. An elastomeric adapter sleeve has an outer surface complementarily radially outwardly engaging the wall surface, an inner surface snugly surrounding and engaging a conduit passing axially through the passage, and an axially open and annular groove between the surfaces and of a predetermined radial width in a relaxed condition of the sleeve. An annularly continuous tightening ring of a radial dimension greater than the width of the groove fits so tightly in the groove as to press the sleeve radially outward against the surface of the passage and inward against the conduit.
U.S. Pat. No. 3,548,079 of Jones describes such a system wherein the tightening ring is of triangular section, isosceles with an axially extending base and is formed, like the groove in the sleeve, with a screwthread. Thus this ring can be screwed into the sleeve to expand it radially as described above. In addition at least one end of the sleeve is constituted so it can be heat-shrunk around the conduit.
Thus such a feedthrough seal must be radially relatively thick, so that it can accommodate a relatively thick ring on its outside face. Too thin a sleeve will only seal adequately at the outer side, and will not seal at all on the opposite, inside end. The parts of such an arrangement are so difficult to mold and are of such complex construction that these feedthrough fittings are quite expensive. In addition it is fairly complex to mount such an arrangement, as the conduit must be passed through the tightening ring before being poked through the rest of the fitting, a step often forgotten so the installer neglects to seal the joint.